Endovascular devices and methods for exploiting intramural space

ABSTRACT

Devices and methods for the treatment of chronic total occlusions are provided. One disclosed embodiment comprises a method of facilitating treatment via a vascular wall defining a vascular lumen containing an occlusion therein. The method includes providing a first intravascular device having a distal portion with a concave side, inserting the first device into the vascular lumen, positioning the distal portion in the vascular wall, and orienting the concave side of the distal portion toward the vascular lumen.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a continuation application of U.S.application Ser. No. 13/304,157, filed Nov. 23, 2011, which is acontinuation of U.S. application Ser. No. 11/518,429, filed Sep. 11,2006, now U.S. Pat. No. 8,083,727, which claims the benefit of U.S.Provisional Application No. 60/811,478, filed Jun. 7, 2006, under 35U.S.C. §119(e). In addition, the application also claims the benefit ofU.S. Provisional Application No. 60/727,819, filed Oct. 18, 2005, under35 U.S.C. §119(e). In addition, the application also claims the benefitof U.S. Provisional Application No. 60/717,726, filed Sep. 15, 2005,under 35 U.S.C. §119(e). In addition, the application also claims thebenefit of U.S. Provisional Application No. 60/716,287, filed Sep. 12,2005, under 35 U.S.C. §119(e). The entire disclosure of each of theabove-referenced applications is incorporated by reference herein.

FIELD OF THE INVENTION

The inventions described herein relate to endovascular devices andmethods. More particularly, the inventions described herein relate todevices and methods for exploiting intramural (e.g., subintimal) spaceof a vascular wall to facilitate the treatment of vascular disease. Forexample, the inventions described herein may be used to cross a chronictotal occlusion and facilitate treatment of the occluded vessel byballoon angioplasty, stenting, atherectomy, or other endovascularprocedure.

BACKGROUND OF THE INVENTION

Due to age, high cholesterol and other contributing factors, a largepercentage of the population has arterial atherosclerosis that totallyoccludes portions of the patient's vasculature and presents significantrisk to the patient's health. For example, in the case of a chronictotal occlusion (CTO) of a coronary artery, the result may be painfulangina, loss of functional cardiac tissue or death. In another example,complete occlusion of the femoral or popliteal arteries in the leg mayresult in limb threatening ischemia and limb amputation.

Commonly known endovascular devices and techniques for the treatment ofchronic total occlusions (CTOs) are either inefficient (resulting in atime consuming procedure), have a high risk of perforating a vessel(resulting in an unsafe procedure), or fail to cross the occlusion(resulting in poor efficacy). Physicians currently have difficultyvisualizing the native vessel lumen, cannot accurately directendovascular devices toward the visualized lumen, or fail to advancedevices through the occlusion. Bypass surgery is often the preferredtreatment for patients with chronic total occlusions, but surgicalprocedures are undesirably invasive.

SUMMARY OF THE INVENTION

To address this and other unmet needs, the present invention provides,in exemplary non-limiting embodiments, devices and methods forexploiting intramural (e.g., subintimal) space of a vascular wall tofacilitate the treatment of vascular disease. For example, the devicesand methods disclosed herein may be used to (i) visually define thevessel wall boundary; (ii) protect the vessel wall boundary fromperforation; (iii) bypass an occlusion; and/or (iv) remove an occlusion.Embodiments are described herein which perform these functionsindividually as well as collectively. These embodiments may be used inthe treatment of a variety of vascular diseases such as chronic totalocclusions in the coronary and peripheral arteries, but are notnecessarily limited in terms of vascular site or disease state.

The embodiments presented herein are generally described in terms of usein the subintimal space between the intima and media for purposes ofillustration, not necessarily limitation. It is contemplated that theseembodiments may be used anywhere in the vascular wall (i.e., intramural)or between the vascular wall and an adjacent occlusion. It is alsocontemplated that these embodiments may operate at one or moreintramural locations, and may operate within the outer limits of thevascular wall to avoid perforation out of the wall and into thepericardial space.

In one embodiment, devices and methods are disclosed herein whichvisually define the vessel wall boundary across an occlusion byplacement of a circumferential radiopaque element in the subintimalspace. In another embodiment, devices and methods are disclosed hereinwhich protect the vessel wall boundary from perforation by a devicepassing through an occlusion by placement of a circumferential guardelement in the subintimal space. In yet another embodiment, devices andmethods are disclosed herein which bypass an occlusion by entering thesubintimal space proximal of the occlusion, safely passing through thesubintimal space past the occlusion, and re-entering the native lumendistal of the occlusion. Other embodiments exploiting the subintimalspace are also disclosed.

BRIEF DESCRIPTION OF THE DRAWINGS

It is to be understood that both the foregoing summary and the followingdetailed description are exemplary. Together with the following detaileddescription, the drawings illustrate exemplary embodiments and serve toexplain certain principles. In the drawings:

FIG. 1 is a schematic illustration of a heart showing a coronary arterythat contains a total occlusion:

FIG. 1A is a detailed view of the coronary artery and total occlusionshown in FIG. 1;

FIG. 1B is a fluoroscopic representation of the view shown in FIG. 1A;

FIG. 2 is a schematic representation of a coronary artery showing theintimal, medial and adventitial layers;

FIG. 3A is a longitudinal cross-section of an artery with a totalocclusion showing a device deployed in the subintimal space:

FIG. 3B is a fluoroscopic representation of the deployed subintimaldevice;

FIG. 4 is a schematic illustration of a device for deploying thesubintimal device in a helical pattern;

FIG. 4A is a cross-sectional view taken along line A-A in FIG. 4;

FIG. 4B is a cross-sectional view taken along line B-B in FIG. 4;

FIG. 5 is a longitudinal cross-section of an artery with a totalocclusion showing a delivery device deploying a subintimal device in ahelical pattern within the subintimal space;

FIG. 6 is a schematic illustration of an alternative subintimal devicethat may assume a helical pattern itself;

FIGS. 7A-7D schematically illustrate alternative subintimal deviceembodiments;

FIGS. 8A and 8B schematically illustrate a system that utilizes fluid toachieve atraumatic passage and promote dissection in the subintimalspace;

FIGS. 9A-9J schematically illustrate various embodiments of torsionallyrigid yet flexible designs for a subintimal device;

FIGS. 10A-10D schematically illustrate various embodiments of threadeddesigns for a subintimal device;

FIGS. 11A-11C schematically illustrate various over-the-wire embodimentsfor a subintimal device;

FIGS. 12A-12C schematically illustrate various directing devices fordirecting a subintimal device to engage and penetrate the intimal layerand enter the subintimal space;

FIGS. 13A-13B schematically illustrate a subintimal device capable ofdissection by actuation;

FIGS. 14A-14H schematically illustrated the steps involved in bypassinga total occlusion via the subintimal space;

FIGS. 15A and 15B schematically illustrate an embodiment for orientingand reentering the true lumen;

FIGS. 16A-16D schematically illustrate an alternative embodiment fororienting and reentering the true lumen;

FIGS. 17, 17A and 17B illustrate a subintimal device having a mating orkeying feature for torque transmission;

FIG. 18 illustrates an alternative subintimal device;

FIGS. 19A and 19B illustrate a subintimal device having a compound bendto facilitate orientation;

FIG. 20A illustrates an alternative subintimal device capable ofachieving a compound bend;

FIG. 20B illustrates a laser cut pattern for a Nitinol tube for use inthe device shown in FIG. 20A;

FIGS. 21A and 21B illustrate another alternative subintimal devicecapable of achieving a compound bend;

FIGS. 22A-22C illustrate yet another alternative subintimal devicecapable of achieving a compound bend;

FIGS. 23A-23E illustrate various re-entry device embodiments;

FIGS. 24A-24C illustrate various penetration mechanisms for a re-entrydevice;

FIG. 25 schematically illustrates a system for confirming true lumenre-entry;

FIGS. 26A and 26B schematically illustrate a subintimal deployableelement and delivery system therefor;

FIG. 27 illustrates the use of a subintimal deployable element forguarding against perforation;

FIG. 28 schematically illustrates an alternative subintimal deployableelement;

FIGS. 29A-29D illustrate a subintimal device including an accessorysubintimal deployable element;

FIGS. 30A-30D and 31A-31B illustrate various devices that facilitateocclusion removal after subintimal delamination; and

FIGS. 32A-32E illustrate an alternative system for bypassing a totalocclusion.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

The following detailed description should be read with reference to thedrawings in which similar elements in different drawings are numberedthe same. The drawings, which are not necessarily to scale, depictillustrative embodiments and are not intended to limit the scope of theinvention.

Introduction

Generally, the various embodiments described herein exploit thesubintimal space in a vascular wall for purposes of facilitatingtreatment of vascular disease. In the following detailed description,the embodiments have been organized in terms of their particularfunction: (i) visually defining the vessel wall boundary; (ii) guardingthe vessel wall boundary from perforation; (iii) bypassing an occlusion;and (iv) alternative functions. This organizational approach is used forpurposes of illustration and explanation, not for purposes oflimitation, as some aspects of some embodiments may be utilized for morethan one of the stated functions, and many embodiments have alternativefunctions not specifically stated or reflected by the organizationaltitles.

In order to understand the methods by which the embodiments describedherein advantageously exploit the subintimal path, it is helpful tofirst understand the anatomical structures at hand.

Relevant Anatomy

With reference to FIG. 1, a diseased heart 100 is shown schematically.Heart 100 includes a plurality of coronary arteries 110, all of whichare susceptible to occlusion. Under certain physiological circumstancesand given sufficient time, some occlusions may become total or complete,such as total occlusion 120.

As used herein, the terms total occlusion and complete occlusion areintended to refer to the same or similar degree of occlusion with somepossible variation in the age of the occlusion. Generally, a totalocclusion refers to a vascular lumen that is 90% or more functionallyoccluded in cross-sectional area, rendering it with little to no bloodflow therethrough and making it difficult or impossible to pass aconventional guide wire therethrough. Also generally, the older thetotal occlusion the more organized the occlusive material will be andthe more fibrous and calcified it will become. According to one acceptedclinical definition, a total occlusion is considered chronic if it isgreater than two (2) weeks old from symptom onset.

With reference to FIG. 1A, a magnified view of total occlusion 120within coronary artery 110 is shown schematically. Generally, theproximal portion 112 of artery 110 (i.e., the portion of artery 110proximal of total occlusion 120) may be easily accessed usingendovascular devices and has adequate blood flow to supply thesurrounding cardiac muscle. The distal portion 114 of artery 110 (i.e.,the portion of artery 110 distal of total occlusion 120) is not easilyaccessed with interventional devices and-has significantly reduced bloodflow as compared to proximal portion 112.

A commonly performed diagnostic procedure called an angiogram involvesthe infusion of a radiopaque fluid into the arterial bloodstream througha percutaneously placed angiography catheter. Using an x-rayfluoroscope, two-dimensional images of the arterial pathways may beobtained and recorded. FIG. 1B shows a schematic example of anangiographic image of a chronic total occlusion 120. It is common thatthe angiogram allows a physician to visualize the proximal segment 112but does not allow visualization of the occlusion 120 or the distalsegment 114. With reference to FIG. 2, a cut-away segment of coronaryartery 110 is shown schematically. Coronary artery 110 includes a trueor native lumen 116 defined by arterial wall 118. The innermost layer ofarterial wall 118 is called the intima or intimal layer 113 (for sake ofclarity, the multi layer intima is shown as a single homogenous layer).Concentrically outward of the intima is the media or medial layer 115(which also is comprised of more than one layer but is shown as a singlehomogenous layer). The outermost layer of the artery is the adventitia117. The transition between the outermost portion of the intima and theinnermost portion of the media is referred to as the subintimal space,which may be delaminated to increase the space therebetween. Thesubintimal space is sometimes referred to as a false lumen, in contrastto true lumen 116.

Visualization & Perforation Guard Embodiments

As may be appreciated from FIG. 1B, a total occlusion 120 prevents theocclusion and distal arterial segment 114 from being visualized usingradiopaque contrast media injection fluoroscopy. In some instances,sufficient contrast media may pass through collaterals around the totalocclusion 120 to achieve visualization of the distal segment 114, butvisualization of the distal segment 114 is often unclear andvisualization of the occluded segment 120 is still not achieved. In somerare instances, sufficient radiopaque contrast may be injectedretrograde through the venous system to achieve a fluoroscopic image ofthe distal segment 114, but such images are often hazy and still do notilluminate the occluded segment 120.

To achieve visualization of the occluded segment 120 and the distalsegment 114, a radiopaque subintimal device 300 may be introduced intothe subintimal space as shown in FIG. 3A. In this illustration,subintimal device 300 is intended to be relatively generic, as a varietyof subintimal devices may be employed as will be described in moredetail hereinafter. The subintimal device 300 exits the true lumen 116and enters the subintimal space 130 at entry point 132 proximal of thetotal occlusion 120 somewhere in the proximal segment 112. Within thesubintimal space 130, the subintimal device 300 may extend across andbeyond the total occlusion 120 and into the distal segment 114. With thesubintimal device positioned as shown in FIG. 3 A, and due to theradiopaque nature of the subintimal device 300, the occluded segment 120and distal segment 114 may be fluoroscopically visualized as shown inFIG. 3B.

Thus, subintimal device 300 may be used to enhance arterialvisualization by placement within the subintimal space 130concentrically around the total occlusion 120. The subintimal device 300defines the approximate inside diameter of the artery 110 and alsodefines axial bends or tortuosity in the vessel 110 across the occludedsegment 120 and distal segment 114. thereby defining the circumferentialboundary of the artery 110 across the occluded segment 120 and distalsegment 114. Also, by placement within the subintimal space 130concentrically around the total occlusion 120, the subintimal device 300may be used to protect or guard the wall 118 of the artery 110 fromperforation of devices that attempt to penetrate the total occlusion 120via the true lumen 116.

As shown in FIGS. 3A and 3B, the subintimal device 300 is deployed in ahelical pattern within the subintimal space 130. The helical pattern isshown for purposes of illustration, not limitation, as other patternsmay be employed as well. Various other deployment patterns are describedin more detail hereinafter, but the helical pattern is used herein tofurther illustrate the concept.

With reference to FIGS. 4, 4A and 4B, a deployment device 400 is shownschematically. Deployment device 400 may be used to direct thesubintimal device 300 into the subintimal space 130 at entry point 132and deploy the subintimal device 300 in a helical pattern therein asshown in FIG. 5. The deployment device 400 may take the form of aballoon catheter including catheter shaft 402 and distal balloon 404.Catheter shaft 402 includes an outer tube 406 and an inner tube 408defining an inflation lumen 410 therebetween for inflation of balloon404. The inner wire tube 408 defines a guide wire lumen 412 therein foradvancement of the device 400 over a guide wire (not shown). A deliverytube 414 extends along the outer tube 406 and around the balloon 404 ina helical (or other) pattern. The delivery tube 414 defines a deliverylumen 416 therein for advancement of the subintimal device therethrough.In this particular embodiment, the subintimal device 300 may have astraight configuration in its relaxed state and rely on the helicaldelivery tube 414 to achieve the desired helical pattern.

With reference to FIG. 5, the delivery device 400 is shown in positionjust proximal of the total occlusion 120. In this position, the balloon404 may be inflated within the vessel lumen 116 to direct the deliverytube 414 toward the vessel wall 118 at an orientation for the subintimaldevice 300 to penetrate through the intima 113 at an entry point andinto the subintimal space. By-virtue of the helical delivery tube 414,the subintimal device 300 is sent on a helical trajectory as it isadvanced through delivery tube 414 resulting in deployment of thesubintimal device 300 in a helical pattern. As shown, the subintimaldevice 300 has been advanced through the delivery tube 414 andpositioned concentrically outside the total occlusion 120, outside theintimal layer 113, and inside the medial layer 115 in the subintimalspace.

With reference to FIG. 6, an alternative approach to achieving a helicalpattern in the subintimal space is shown. Whereas the delivery device400 described previously provided a helical delivery tube to deliver asubintimal device 300 that had a straight configuration in its relaxedstate, FIG. 6 schematically illustrates an alternative subintimal device600 that may assume a helical shape itself. Subintimal device 600includes an elongate tubular shaft 604, at least a distal portion ofwhich includes a helical interlocking gear 606 and a helical wire coil608 disposed thereon. A helically shaped inner mandrel or tube 610 maybe disposed in the tubular shaft 604 such that the shaft 604 rotatesfreely thereon. The shaft 604 may have a linear or straightconfiguration in a relaxed state and a helical configuration (shown)when the helically shaped inner member 610 is disposed therein. Thedevice 600 may be disposed in a constraining sheath (not shown) andnavigated to the intravascular site, such as the site of a totalocclusion. When the device 600 is advanced distally out the end of theconstraining sheath or when the sheath is pulled proximally relativethereto, the distal portion of the device 600 assumes a helical shape asshown. The shaft 604 may be rotated relative to the inner member 610 tocause rotation of the helical wire threads 608, which may be used toengage the vessel wall and advance around the total occlusion in thesubintimal path. A bearing (not shown) may be disposed on the innermember 610 to engage the proximal or distal end of the shaft 604 toenable the shaft 604 and the inner member 610 to be advanced in unison.Subintimal device 600 may include any of the variants describedhereinafter, such as various gear shaft configurations, distalatraumatic tip configurations, fluidic dissection mechanisms, etc.

Generally, the subintimal devices described herein are designed forintravascular navigation and atraumatic subintimal passage. Thesubintimal devices 300 may be constructed similar to a guide wire andmay include elements to atraumatically pass through the subintimalspace. Such atraumatic elements may be employed to minimize damage toarterial wall and to minimize the likelihood of perforationtherethrough. Examples of such atraumatic elements 310 are schematicallyillustrated in FIGS. 7A-7C. The subintimal device may include aball-shaped tip 310A as shown In FIG. 7A, a hook-shaped or loop-shapedtip 310B as shown in FIG. 7B, and/or a bent tip 310C as shown in FIG.7C. These atraumatic elements distribute axial forces over larger areasof tissue and thereby reduce the chance of vessel perforation. Anadditional aspect of the bent tip 310C is ability to torsionally directthe tip and control the path of the device through the subintimal space.The ball tip 310A may be formed from a suitable metallic materialincluding but not limited to stainless steel, silver solder, or braze.The ball tip 310A may also be formed from suitable polymeric materialsor adhesives including but not limited to polycarbonate, polyethylene orepoxy. Note that the ball tip 310A may be bulbous and larger than theshaft proximal thereto. The loop tip 310B and bent tip 310C may becreated during the manufacturing process (for example by heat setting ormechanical deformation) or the tip may be shaped (for example bymechanical deformation) by the physician.

As an alternative or in addition to the atraumatic tip elements 310 asdescribed above, the subintimal device 300 may use a guide wire 700 tofacilitate atraumatic passage as shown in FIG. 7D. In this embodiment,the subintimal device 300 may include a lumen extending therethroughsuch that the device 300 may be advanced over the guide wire 700. Inthis embodiment, the body of the subintimal device 300 has a hollowinternal diameter defining a guide wire lumen therein. The guide wirelumen extends from a proximal opening to a distal opening and is sizedto accept a guide wire 700 therethrough. The guide wire 700 provides anatraumatic element at its distal end and also provides a mechanism forrotationally steering the subintimal device 300 through the subintimalspace. The guide wire 700 may be pushed forward by the subintimal devicethrough a bearing element (not shown) at the proximal or distal end ofthe subintimal device. The bearing element may provide interference inthe axial direction while allowing for relative rotation between thesubintimal device and guide wire. An example of a bearing element may bea collar crimped to the distal end of the guide wire with an outsidediameter larger in dimension than the guide wire lumen within thesubintimal device.

Other techniques may be employed to facilitate atraumatic passagethrough the subintimal space. For example, pressurized fluid may be usedto facilitate atraumatic passage and even promote atraumatic dissectionof the layers defining the subintimal space. FIGS. 8A and 8Bschematically illustrate a system 800 that utilizes fluid to achieveatraumatic passage and promote dissection. System 800 includes asubintimal device 810 and associated pumping system 820. The fluidicsystem 800 is similar in certain aspects to the arrangements describedelsewhere herein, the various aspects of which may be combined or usedin the alternative as will be appreciated by those skilled in the art.System 800 includes a subintimal device 810 which may comprise any ofthe tubular subintimal devices described herein. Generally, subintimaldevice 810 includes a tubular shaft 812 having a proximal end connectedto a pumping mechanism 820. A plunger rod 814 is slidably disposed inthe tubular shall 812 as shown in FIG. 8B and its proximal end isconnected to a linear actuator 822 of the pumping mechanism as shown inFIG. 8A. The rod 814 extends through the tubular shaft 812 to a pointproximal of the distal end thereof to define a pumping chamber 816. Asource of liquid 830 (e.g., saline bag) is connected to the proximal endof the subintimal device 810 via a fluid line 832 and optional valve 834to supply liquid to the annular lumen between the rod 814 and the innerwall of the tubular shaft 812. As the linear actuator moves the rod 814back and forth in the tubular shaft 812, liquid is caused to be expelledout of the chamber 816 in a pulsatile fashion. which may be used tohydraulically dissect tissues to define a subintimal path as describedpreviously, for example. Optionally, a balloon may be disposed on thedistal end of the device such that it is cyclically inflated anddeflated with the pulsatile flow to cause controlled dissection. Thestroke length, stroke rate and stroke volume may be adjusted to achievethe desired effect. For example, the stroke volume of the chamber 816may be relatively small (0.01 cc-1.0 cc, for example) such that liquidexits the chamber 816 with high energy that dissipates quickly tominimize trauma to tissues as they are dissected. One example is astroke volume of 0.25 cc and a stroke rate of 10 Hz which has been foundto facilitate atraumatic passage and even promote atraumatic dissectionin a bench-top model using animal tissues.

Another technique to facilitate or supplement atraumatic passage of thesubintimal device is to reduce friction between the device and thesurrounding tissues. The fluidic embodiment described above benefitsfrom this technique in that saline acts to reduce friction. Friction mayalso be reduced by using coatings (e.g., PTFE. hydrophilic materials,etc.) which may be applied to the external surface of the subintimaldevice. Friction may also be reduced by taking advantage of the factthat the kinetic coefficient of friction is usually less than the staticcoefficient of friction for a given frictional interface. As applied tothe subintimal devices described herein, the lower kinetic coefficientof friction may be utilized by rotating the device back and forthbetween tissues in the subintimal space. Such reciprocal rotationalmotion may be applied manually by rolling the proximal end of the devicebetween the user's thumb and forefinger, or may be applied usingautomatically using a reciprocal motor drive, for example.

Whether it is to reduce friction, to facilitate steering. or tofacilitate advancement, it may be desirable to incorporate enhancedtorsional characteristics in the body 302 of the subintimal device 300as schematically shown in FIGS. 9A-9F. Generally, it is desirable tomaintain flexibility of at least a distal portion of the body 302 toavoid compromising intravascular navigation in tortuous pathways. FIG.9A schematically shows a generic subintimal device 300 with a distalbody portion 302 and a proximal body portion 304. Relative to theproximal body portion 304, the distal body portion may be more flexiblesince it will frequently encounter a tortuous pathway. The proximal bodyportion may only encounter minimal bends in a guide catheter or thelike, and therefore may be made more stiff yet torsionally rigid as witha metal tube (e.g., stainless steel hypotube).

One example of a flexible yet torsionally rigid distal body 302 designis shown in FIGS. 9B and 9C. In this embodiment, distal body portion 302is made of a multitude of independent coils 902, 904, 906 concentricallywound in opposing directions. These coils can diametrically interact(for example internal coil diametrically expands while the external coildiametrically contracts) with an applied torque. This interaction canprovide torsional strength while maintaining axial flexibility. The coreof the distal body 302 may be hollow or may contain a fixed wire 910within its internal lumen. The fixed wire 910 may provide an increase inaxial and/or torsional stiffness, and may also have a taperingcross-section to increase flexibility in the distal direction. A hollowcore may be used for insertion of a guide wire. Coils 902, 904, 906 andcore wire 910 may be made of suitable metallic or polymeric materialsincluding but not limited to stainless steel, nickel titanium, platinumor ultra high molecular weight polyethylene.

Another example of a flexible yet torsionally rigid distal body 302design is shown in FIG. 9D wherein a single coil 908 is wound over aninternal core 910 surrounded by a thin polymeric sheath 920. Yet anotherexample of a flexible yet torsionally rigid distal body 302 design isshown in FIGS. 9E, and 9F wherein the body simply comprises a singleopen wound coil 912.

A further example of a flexible yet torsionally rigid distal body 302design is shown in FIG. 9G. The distal body 302 may be constructed inpart or in to total of a single layer coil with geometric features alongthe coil length that allow adjacent coils to engage (for examplemechanical engagement similar to the teeth of a gear). FIG. 9G showscoil 930 closely wound with a multitude of teeth 932 along the coiledges in contact such that the peaks of one coil falls within thevalleys of the adjacent coil. A conventional coil (without teeth) reactsto an applied torsional load by diametrically expanding or contracting,thus forcing the wire surfaces within a turn of the coil to translatewith respect to its neighboring turn. The construction of coil 930resists the translation of wire surfaces within the coil thus resistingthe diametric expansion or contraction (coil deformation). An increasedresistance to coil deformation increases the torsional resistance of thedevice body while the coiled construction provides axial flexibility.

This design may be implemented in manner shown in FIG. 9H. Thesubintimal device 300 includes a proximal body portion 304 that isformed of a continuous solid metallic tube 940 and a distal body portion302 that is formed of the same tube with a laser cut coil segment 930,wherein the pattern of the laser cut defines the teeth 932. Suitablematerials for the metallic tube include but are not limited to stainlesssteel and nickel titanium. Alternatively, the coil 930 may be wound froma continuous wire. The wire may have a cross section that for examplehas been mechanically deformed (stamped) to form the teeth 932 and allowcoil engagement.

FIG. 9I shows one example of a laser cut pattern from the circumferenceof a tube that has been shown in a flat configuration for purposes ofillustration. In the pattern shown in FIG. 9I, the teeth 932 aregenerally trapezoidal and extend orthogonal to the coil turns 930. FIG.9J shows an alternative pattern wherein the teeth are generallyrectangular (with a clipped corner) with a major (longer) lengthextending parallel to the axis of the body. The parallel orientation andlonger length of the teeth 932 shown in FIG. 9J promote engagement andreduce slippage of adjacent coil turns 930.

As mentioned previously, another application of a flexible yettorsionally rigid subintimal device is to facilitate advancement throughthe subintimal space using threads that rotationally engage vasculartissues similar to a threaded screw. FIG. 10A shows a subintimal device300 wherein at least the distal body portion 302 includes threads 1000on the exterior surface thereof. The threads 1000 act like an externalcorkscrew that has the ability to rotationally engage the arterialtissues and help drive the subintimal device 300 through the subintimalspace. FIGS. 10B-10D are cross-sectional views taken along line A-A inFIG. 10A and show various alternative embodiments for the threads 1000.FIG. 10B shows one or more round corkscrew members 1010 that areconcentrically wound on the outside of the distal body 302. FIG. 10Cshows a multi-layer coil construction with coil layers 902, 904, 906where corkscrew member 1020 comprises a wire element of larger crosssectional area wound within the external concentric coil 906. Thecorkscrew members may have a rounded shape as shown in FIGS. 10B and10C, or other shape such as triangular, square, or other cross-sectionalshape that may aid in tissue engagement and subintimal deviceadvancement. FIG. 10D) shows a polymer tube with a corkscrew profile1030 formed therein and concentrically positioned around distal bodyportion 302. In each of these embodiments, withdrawal of the subintimaldevice 300 may be achieved by rotating the device in the oppositedirection thus driving the device back out of the subintimal space.

In some instances, it may be desirable to utilize an over-the-wire typesubintimal device to facilitate advancement into and through thesubintimal space. In addition to the embodiments described previously,FIGS. 11A-11C illustrate additional over-the-wire type embodiments ofsubintimal devices. These embodiments may also be used to facilitateguide wire advancement through a total occlusion, such as when it isdesirable to stay in the true lumen.

FIG. 11A shows an over-the-wire type subintimal device 1100 (or wiresupport device) having a coiled gear design 930 as described withreference to FIGS. 9G-9J and a thread design 1000 as described withreference to FIGS. 10A-10D. The device 1100 has a hollow core and may beadvanced over a guide wire 700. The geared coils 930 provide axialflexibility and torsional rigidity and the external helical threadsprovide mechanical engagement with the lesion or arterial wall. FIG. 11Bshows an over-the-wire type subintimal device 1110 (or wire supportdevice) in longitudinal section, with an inner tube 1112 having a coiledgear design 930. and an outer tube 1114 having a thread design 1000. Theinner tube 1112 contains a guide wire lumen capable of accepting aconventional guide wire 700. FIG. 11C shows a partial enlarged view ofan alternative inner tube 1112 where gaps 934 between adjacent coilsallow articulation of the inner tube 1112 upon proximal withdrawal ofactuation wire 1118. Outer tube 1114 may freely rotate with respect toinner tube 1112 when the inner tube 1112 is in both the straight andactuated positions.

In the foregoing embodiments, the subintimal device enters thesubintimal space via an entry point. In other words, the subintimaldevice extends from the true lumen and into the subintimal space throughthe entry point. This may be accomplished by directing a subintimaldevice toward the intimal layer and penetrating therethrough.Alternatively, a guide wire may be used to penetrate the intimal layerand enter the subintimal space. This latter approach may be morecommonly employed since physicians often find themselves unintentionallyentering the subintimal space with a guide wire. However, to facilitatedefinitive exploitation of the subintimal space, the embodimentsdescribed herein intentionally facilitate penetration of the intimallayer and entry into the subintimal space, which is contrary toconventional current practice.

It is contemplated that a bare guide wire (i.e., a guide wire without adirecting catheter) using a bent tip at a length and angle sufficient toengage the intima away from the true lumen, may be used to intentionallypenetrate the intima and enter the subintimal space. However, adirecting catheter may be employed to consistently and predictablyfacilitate entry into the subintimal space. As illustrated in FIGS.12A-12C, various directing devices may be used to direct the subintimaldevice (or guide wire over which the subintimal device is advanced) toengage and penetrate the intimal layer and enter the subintimal space.

FIG. 12A schematically illustrates a directing catheter 1200substantially similar to an over-the-wire balloon catheter including adistal balloon 1220 with the addition of a delivery and directing tube1210. As shown, the directing catheter 1200 has been advanced over aconventional guide wire 700 and inflated proximal to the total occlusion120. For the sake of clarity, FIG. 12A shows a subintimal device paththat is substantially parallel to the vessel lumen, but otherorientations (e.g., helical) may also be employed. The delivery anddirecting tube 1210 may be positioned adjacent to and pointed slightlyoutward and toward the intimal layer 113 such that the subintimal device300 may be advanced to perforate the subintimal layer 113. A fluidsource (e.g., syringe) 1230 may be connected to be in fluidcommunication with the delivery and directing tube 1210 via an infusiontube 1232. Fluid may flow from the fluid source 1230 through thedelivery and directing tube 1210 under a controlled pressure or acontrolled volume. The infused fluid may enter the subintimal space 130directly from the delivery and directing tube 1210 or from the truelumen 116 space defined between the distal end of the balloon 1220 andthe proximal edge of the occlusion 120. The fluid may be radiopaquecontrast media to facilitate fluoroscopic visualization of thesubintimal space, and/or may be used to delaminate the intimal layer 113and medial layer 115 defining the subintimal space 130. FIG. 12Bschematically illustrates an alternative embodiment of directingcatheter 1200 wherein the fluid source 1230 is in fluid communicationwith a lumen within the subintimal device 300 thereby directly infusingfluid into the subintimal space 130 via subintimal device 300. FIG. 12Cschematically illustrates another embodiment wherein the directingcatheter 1250 is similar to a subselective guide catheter wherein thedistal end 1252 has a predefined shape or an actuating element thatallows manipulation by the physician intra-operatively to direct thesubintimal device 300 toward the intimal layer for penetrationtherethrough.

Once the subintimal device is in the subintimal space, the intima may bedelaminated from the media to open the subintimal space by bluntdissection as the subintimal device is being advanced. Alternatively,the intima may be delaminated from the media using pressurized fluid asdescribed previously. As a further alternative, the layers may bedelaminated by actuation as illustrated in FIGS. 13A and 13B. Subintimaldevice 1300 may be actuated or self-expanded between a collapsedconfiguration shown in FIG. 13A and an expanded configuration shown inFIG. 13B. The device 1300 may be advanced in a collapsed state untilresistance is felt, and then expanded to delaminate layers in theexpanded state in order to propagate the subintimal dissection. Thesubintimal device 1300 may comprise a shaft 1310 having a plurality ofresilient expandable elements 1312 (e.g., heat set NiTi) and anatraumatic tip 1314 (shown bent). A sheath 1320 may be disposed aboutthe proximal shaft 1310 and the expandable elements 1312 to retain theexpandable elements 1312 in a collapsed configuration as shown in FIG.13A. Upon proximal refraction of the sheath 1320 (or distal advancementof the shaft 1310) the expandable elements 1312 elastically expand asshown in FIG. 13B to cause propagation of the dissection. The sheath1320 may be advanced to collapse the expandable elements 1312 and thedevice 1300 may be advanced further into the subintimal space.Alternatively, the actuation mechanism may comprise an inflatableballoon that dissects when inflated and is advanceable when deflated.

Bypass Embodiments

The foregoing embodiments generally involve penetrating the intimallayer, placing a subintimal device in the subintimal space, andtraversing across the occluded segment for purposes of defining thevascular boundary and/or for purposes of guarding against perforation.The following bypass embodiments also involve the initial steps ofpenetrating the intimal layer, placing a subintimal device in thesubintimal space, and traversing across the occluded segment. To thisend, the devices and methods described with reference to boundarydefinition and perforation guard embodiments have application to thefollowing bypass embodiments.

In addition to penetrating the intimal layer, entering the subintimalspace, and traversing the occluded segment, the following bypassembodiments generally involve orientation and re-entry into the truelumen. A general approach to the foregoing bypass embodiments isschematically illustrated in FIGS. 14A-14H. A guide wire 700 may beadvanced through the proximal segment 112 of the true lumen 116 of theoccluded artery to the proximal edge of the total occlusion 120 adjacentthe vessel wall 118 as shown in FIG. 14A. By manipulating and directingthe guide wire 700 to (the proximal edge of the total occlusion 120toward the wall 118, the guide wire 700 may penetrate the intimal layer113 and enter the subintimal space 130 between the intima 113 and themedia/adventitia 115/117 as shown in FIG. 14B. The manipulating anddirecting of the guide wire 700 as described above may be performed byusing the guide wire alone or by using any of the directing devicesdescribed herein. With the guide wire 700 in the subintimal space 130, asubintimal device 1400 may be advanced over the guide wire 700 as shownin FIG. 14C. In the illustrated embodiment, the subintimal device 1400includes a hollow elongate shaft 1402 and an atraumatic bulbous tip1404. However, any of the subintimal devices described herein may beemployed, particularly the over-the-wire type subintimal devices. Asshown in FIG. 14D, the subintimal device 1400 may be further advancedover the guide wire 700 such that the tip 1404 resides in the subintimalspace 130. At this procedural stage, the guide wire 700 may bewithdrawn, completely removing it from the subintimal device 1400.Further manipulation of the subintimal device 1400 (both axialadvancement and radial rotation) allows blunt dissection of the layersdefining the subintimal space 130 and advancement of the device 1400 tothe distal portion of the total occlusion 120 as shown in FIG. 14E.Penetration of the intimal layer 113 and re-entry into the distalsegment 114 of the true lumen 116 distal to the occlusion 120 may beachieved by various means described later in detail, which generallyinclude the steps of orientation toward the center of the true lumen 116and penetration of the intimal layer 113. For purposes of illustration,not limitation, FIG. 14F shows a shaped re-entry device 1420 having acurled and sharpened tip exiting the lumen of the subintimal device 1400distal of occlusion 120 and entering the distal segment 114 of the truelumen 116 through the intimal layer 113. With re-entry device 1420 inthe distal segment 114 of the true lumen 116, the subintimal device 1400may be advanced into the true lumen 116 over the re-entry device 1420 asshown in FIG. 14G. The re-entry device 1420 may be withdrawn from thesubintimal device 1400 and the guide wire 700 may be advanced in itsplace as shown in FIG. 14H, after which the subintimal device 1400 maybe withdrawn leaving the guide wire 700 in place. As such, the guidewire 700 extends from the proximal segment 112 of the true lumen 116proximal of the occlusion 120, traverses the occluded segment via thesubintimal space 130, and reenters the distal segment 114 of the truelumen 116 distal of the occlusion 120, thus bypassing the totalocclusion 120 without exiting the artery. With the guide wire 700 soplaced, the subintimal space 130 may be dilated (e.g., by balloonangioplasty or atherectomy) and stented, for example, or otherwisetreated using known techniques.

As mentioned above, re-entry into the true lumen from the subintimalspace generally involves orientation toward the center of the true lumenand penetration of the intimal layer. Although fluoroscopy is a commonlyavailable visualization tool used during interventional procedures, itonly provides two-dimensional images which are typically insufficient,taken alone, to determine the proper direction for penetration from thesubintimal space toward the center of the true lumen. As such, thoseskilled in the art may use visualization tools with greater accuracy orwith the ability to show three dimensional data. For example,intravascular ultrasound (IVUS) or magnetic resonance imaging (MRI) maybe used to determine the position and direction of true lumen re-entryfrom the subintimal space. However, such techniques are time consuming,expensive and often impractical, and therefore it would be desirable tofacilitate orientation (i.e., direct a re-entry device from thesubintimal space toward the true lumen distal of a total occlusion)without the need for such burdensome visualization techniques.

Various orientation and re-entry embodiments are described herein thattake advantage of the position and geometry of the subintimal spacerelative to the true lumen to facilitate effective orientation of are-entry device from the subintimal space toward the true lumen. Thismay be accomplished by recognizing that the subintimal space isgenerally annular with its radial center at the center of the truelumen. Thus, a curved device deployed in the subintimal space defines atleast an arc and at most a full circle (in radial cross-section), theradial center of which must reside at the center of the true lumen. Inother words, if a curved device that is deployed in the subintimal spacesuch that the curvature of the device is aligned with the curvature ofthe subintimal space, then the true lumen is by necessity orientedtoward the concave side of the curved subintimal device. A re-entrydevice may then be keyed or otherwise oriented to the concave side ofthe subintimal device, and is thus automatically oriented toward thetrue lumen without visualization.

One such embodiment that operates under this premise is shownschematically in FIGS. 15A and 15B. In this embodiment, a helicalsubintimal device 1500 is shown generically, the features of which maybe incorporated into other subintimal device embodiments describedherein. Subintimal device 1500 generally includes an elongate tubularshaft 1502 having a lumen 1504 extending therethrough and a re-entryport 1506 disposed distally in the region of the helical shape. In thisembodiment, the distal portion of the shaft 1502 may have a helicalshape in its relaxed state such that the re-entry port 1506 is alwaysoriented toward the concave side or center of the helix as shown in FIG.15A. The helical portion may be deployed in the subintimal space aroundthe total occlusion as described elsewhere herein, resulting in theconcave portion of the helix and the port 1506 being oriented toward thetrue lumen. With this arrangement, a re-entry device such as a guidewire 700 or flexible stylet with a tissue penetrating tip may beadvanced through the lumen 1504 of the shaft 1502 to exit the re-entryport 1506 as shown in FIG. 15B. This arrangement may be used toestablish re-entry into the true lumen after the subintimal device 1500has been deployed across an occlusion in the subintimal space.

Other orientation and re-entry embodiments are described herein thattake advantage of the different properties of the layers of the arterywall to facilitate effective orientation of a re-entry device from thesubintimal space toward the true lumen. In some instances, the intima113 is more pliable than the composite of the media 115 and adventitia117. Thus, expansion of an element in the subintimal space 130 willresult in more deflection of the intima 113 than the media 115 andadventitia 117.

One such embodiment that operates under this premise is shownschematically in FIGS. 16A-16D). In this embodiment, a subintimal device(not shown) as described elsewhere herein may be used to pass the totalocclusion and place a guide wire 700 as shown in FIG. 16A. The guidewire 700 extends across the occlusion 120 and is disposed in thesubintimal space 130 between intima 113 and the media/adventitia 115/117where re-entry into the true lumen 116 distal of the occlusion 120 isdesired. A balloon catheter 1620 is then advanced over the guide wire700 until the balloon portion 1622 is disposed adjacent the distal endof the occlusion 120 as shown in FIGS. 16B and 16C. The guide wire 700is pulled proximally and the balloon 1622 is then inflated causingradial displacement of the distal end of the balloon catheter 1620 asshown in FIG. 16C. Inflating the balloon 1622 of the balloon catheter1620 orients the tip of the catheter 1620 toward the intima 113. Theguide wire 700 may be removed from the balloon catheter 1620 and asharpened stylet 1630 or the like may be advanced through the guide wirelumen of the catheter 1620 until the distal end of the stylet 1630penetrates the intima 113 as shown in FIG. 16D. thus establishingre-entry from the subintimal path 130 and into the true lumen 116

Detailed Examples of Bypass Embodiments

In the following embodiments, detailed examples of devices are describedwhich facilitate one or more of the steps involved in visualizing,perforation guarding, and/or bypassing a total occlusion as generallydescribed previously. These devices may, for example: (i) facilitatesubintimal device tracking by transmitting sufficient axial force andradial torque (sometimes referred to as push and twist respectively) toenter the subintimal space, delaminate the intima from surroundingtissue layers, and traverse the total occlusion via the subintimalspace; (ii) facilitate alignment of the subintimal device within thesubintimal space with a favorable orientation for true lumen re-entrydistal of the total occlusion; (iii) facilitate advancement of are-entry element that takes advantage of the subintimal device alignmentand orientation to direct itself toward the true lumen; (iv) facilitatepenetration of the intimal layer to regain access to the true lumendistal of the total occlusion; and/or (v) facilitate confirmation thattrue lumen re-entry has been achieved.

Detailed Examples of Axial Push Force and Radial Torque Embodiments

The embodiments described with reference to FIGS. 17 and 18 illustratefeatures of subintimal devices that facilitate the transmission of pushand twist to enter the subintimal space and advance therein. FIG. 17shows an embodiment of a subintimal device 1700 where the properties ofpush and twist may be provided by an internal stylet 1703 slideablydisposed within the central lumen 1701 of a tubular shaft 1702. Withstylet 1703 removed, the central lumen may also accept a guide wire (notshown).

The tubular shaft 1702 may be made from suitable polymeric materialssuch as polyethylene, nylon, or poly-ether-block-amide (e.g., Pebax™).The tubular shaft 1702 may also have composite structure where theinside layer may have a lubricious polymer such as polyethylene or afluoropolymer such as PTFE (e.g., Teflon™), the middle layer may have ametallic or polymeric braided structure such as polyester or stainlesssteel, while the outside layer may also be made of a similar polymericmaterial. The outside of the subintimal device 1700 may also have alubricious exterior coating. For example, coatings may include liquidsilicone or a hydrophilic coating such as hyaluronic acid. The stylet1703 may be made of suitable metallic materials including but notlimited to stainless steel or nickel titanium alloys. The atraumatic tip1704 may be made of suitable metallic or polymeric materials including,for example, stainless steel, titanium. polycarbonate, orpolyether-block-amide (e.g., Pebax™).

As seen in FIGS. 17A and 17B, which are cross sectional views takenalong lines A-A and B-B, respectively, in FIG. 17, all or a portion(e.g., distal portion) of the stylet 1703 may interface with a feature1706 within the tubular shaft 1702 and/or within the atraumatic tip1704. For example, the tubular shaft 1702 and/or the atraumatic tip 1704may contain a lumen with a geometric feature 1706 intended to mate orkey with distal tip of the stylet 1707 as shown in FIG. 17B. This keyingor mating feature 1706 allows torque to be transmitted from theoperators hand to the distal tip of the subintimal device through twistof the subintimal device and stylet. For the purpose of illustration,the geometric feature 1706 is shown as a square in cross-section, but itis intended that any geometry other than round may be used to createengagement of the perimeter of the stylet 1703 with the internal lumenof the tubular shaft 1702 and/or atraumatic tip 1704.

FIG. 18 shows an embodiment of a subintimal device 1800 having aproximal tubular shaft 1804, a distal tubular shaft 1802, and anatraumatic bulbous tip 1805. In this embodiment, the desired propertiesof push and twist may be provided by constructing the proximal shaft1804 of a rigid material (e.g., metallic hypotube) and constructing thedistal shaft 1802 in a similar manner, for example, to the gear shaftpreviously described with reference to FIG. 9 et seq. Distal gear shaft1802 may be flexible yet torsionally and longitudinally rigid. Thedistal shaft 1802 may be disposed within an outer sheath 1801 and mayhave an internal sheath 1803 as well. The outer and inner sheaths may bemade of suitable polymeric materials such as polyethylene, nylon,polyether-block-amide (e.g., Pebax™), or a fluoropolymer such asTeflon™.

Detailed Examples of True Lumen Orientation Embodiments

The embodiments described with reference to FIGS. 19A-19B, 20A-20B,21A-21B, and 22A-22C illustrate features of subintimal devices thatfacilitate orientation toward the true lumen. Generally, by deploying asubintimal device around at least a portion of the circumference(sometimes referred to as radial bend or curve), the direction of thetrue lumen is toward the center (concave side) of the curve. To achievea radial bend from a longitudinally positioned subintimal device, it maybe necessary or desirable to initially impart an axial bend or curve inthe subintimal device to act as a transitional geometry. Hence, somesubintimal device embodiments described herein have both an axial bend(e.g., FIG. 19A) and a radial bend (e.g., FIG. 19B) when deployed in thesubintimal space. Since the concave side of the radial bend isconsistently toward the true lumen, a re-entry device may be predictablydirected toward the true lumen (without employing complex visualizationtechniques) by aligning itself with respect to the radial curve of thesubintimal device. Thus, in the following embodiments, varioussubintimal device designs are illustrated that accommodate radial bends(and axial bends) to establish the direction of the true lumen towardthe concave side of the radial bend.

FIGS. 19A and 19B show subintimal device 1900 that is capable of aiminga re-entry device (not shown) toward the true lumen 116 distal of atotal occlusion with the aid of standard fluoroscopy. Subintimal device1900 with atraumatic tip 1902 may be positioned within the subintimalspace 130 between the intima 113 and media 115 layers. The subintimaldevice 1900 may be advanced using similar techniques previouslydescribed with reference to FIGS. 14A-14E. Once the subintimal device1900 is in the proper position within the subintimal space 130, a distalportion of the subintimal device 1900 is configured to achieve ageometry having a bend in the longitudinal direction as shown in FIG.19A and a bend in the radial direction as shown in FIG. 19B. Thisthree-dimensional geometry may be referred to as a compound bend. Aswill be described in more detail herein, the compound bend may be usedto facilitate alignment of a re-entry device toward the true lumen 116of the artery 110.

FIG. 20A illustrates a subintimal device 2000, similar to the subintimaldevice 1800 described with reference to FIG. 18, that may be capable ofachieving a compound bend. The subintimal device 2000 includes anelongate tubular shaft 2001 defining an internal lumen, an actuation(e.g., push or pull) member 2003 residing in the lumen of the shaft 2001and having a distal end attached to the distal end of the shaft 2001,and an atraumatic tip 2004 attached to the distal end of the shaft 2001.The flexible yet torsionally rigid distal shaft 2001 has one or moreopen areas 2002 oriented along the actuation member 2003. An externalsheath 2005 may be disposed about the length of the shaft 2001 andactuation member 2003, with its distal end attached to the atraumatictip 2004. For purpose of illustration only, FIG. 20A shows a singleactuation member 2003 in the proximity of a single row of open areas2002 in the shaft 2001. The subintimal device may have one or moreactuation members and may have one or more rows of open areas. Forexample, the shaft 2001 may have a laser cut geometry as shown in FIG.20B with two rows of open areas 2002.

With continued reference to FIG. 20A, a bend may be achieved by pullingthe longitudinal actuation member 2003. Pulling the actuation member2003 partially or completely closes the open spaces 2002 thus shorteningthe length of the shaft 2001 in proximity of the open areas 2002 andcreating a bend in the device 2000. A compound bend may be achievedthrough the use of multiple rows of open areas and/or multiplelongitudinal members 2003. Alternatively, a compound bend may also beachieved using a single row of open areas and a single longitudinalmember by relying on device interaction with the adventitial layer. Inthis alternative, pulling the actuation member 2003 creates the axialcurvature (see FIG. 19A) and interaction with the adventitia may forcethe subintimal device to accommodate a radial curvature (see FIG. 19B).

FIG. 21A shows an alternative embodiment of a subintimal device 2100that may also achieve a compound bend. The subintimal device 2001generally includes an elongate tubular shaft 2102 defining an internallumen 2101, an actuation (e.g., push or pull) member 2105 having adistal end attached to the distal end of the shaft 2102, and anatraumatic tip 2106 attached to the distal end of the shaft 2102. Theshaft 2102 may be constructed from a multitude of alternatingwedge-shaped polymeric segments where segment 2103 may have a lowerdurometer and greater flexibility as compared to the adjacent segment2104. For example, segment 2103 may be made of 4033 Pebax while segment2104 may be 6333 Pebax. These multiple segments may be assembledtogether to make a continuous shaft. For example, the edges of adjacentsegments may be fused together using a process that heats the segmentsabove their melt temperature. The application of heat to segments thatis held in proximity may allow said segments to fuse together. FIG. 21Ashows a series of wedged-shaped segments wherein the relatively stiffsegment 2104 defines a larger percentage of one side along a line of theshaft 2102 while the relatively flexible segment 2103 defines a largerpercentage of the opposing side of the same shaft.

As shown in FIG. 21B, the side of the shaft 2102 with a greaterpercentage of relatively flexible segments 2103 allows more relativecompression upon actuation of member 2105, such that the shaft 2105 mayhave a predisposition to flex to the side with more flexible segmentmaterial 2103 and may have greater resistance to flex to the side withmore stiff segment material 2104. The longitudinal actuation member 2105may be slideably disposed in a lumen within the wall of the shaft 2102and may be attached to the atraumatic tip 2106, extending the length ofthe shaft 2105 and out the proximal end. For purpose of illustration,FIGS. 21A and 21B show a single longitudinal member 2105 in theproximity of a line of relatively flexible segments 2103. The subintimaldevice 2100 may have one or more longitudinal members and may have oneor more lines of flexible segments 2103.

With reference to FIG. 21B a compound bend may be achieved by pullingthe actuation member 2105 relative to shaft 2102. Pulling the actuationmember 2105 may compress segments 2103 thus shortening the subintimaldevice length along the side of the of the shaft 2102 with more flexiblesegment material 2103. A compound bend may be achieved by arranging theflexible segment material 2103 in the desired pattern and/or by usingmultiple longitudinal members 2105. Alternatively, a compound bend mayalso be achieved using a single side of flexible segment material 2103and a single longitudinal member by relying on device interaction withthe adventitial layer as described previously.

With reference to FIGS. 22A-22C, another embodiment of a subintimaldevice 2200 capable of achieving a compound bend is shown schematically.FIG. 22A only shows the distal portion of the subintimal device 2200 forpurposes of illustration and clarity. In this embodiment, the tubularshaft of the subintimal device 2200 comprises an inner tube 2201 and anouter tube 2204 (shown cut away), between which is disposed a series ofcircumferential rings 2202 interconnected by longitudinal members 2203.An atraumatic tip 2207 is connected to the distal end of the shaft, anda central lumen 2206 runs through the device 2200 for the acceptance ofa guide wire and/or a re-entry device. Suitable materials for thecircumferential rings 2202 and longitudinal members 2203 include but arenot limited to nickel titanium, stainless steel, or MP35N. The innertube 2201 and the outer tube 2204 may be made of suitable polymericmaterials such as polyethylene, polyether-block-amide (e.g., Pebax™), ornylon. The distal portion of the subintimal device may have a pre-formedcurved shape (e.g., compound bend) in it's relaxed state as shown inFIG. 22A.

The subintimal device 2200 may be slideably disposed within an externaldelivery sheath 2205 as shown in FIGS. 22B and 22C. The sheath 2205 maybe slightly stiller then the subintimal device 2200 such that thesubintimal device 2200 assumes a straight shape when the sheath 2205covers the distal portion of the device as shown in FIG. 22B, andassumes a curved shape when the sheath 2205 is retracted as shown inFIG. 22A. Upon proximal retraction of the sheath 2205, the subintimaldevice 2200 may assume a compound bend by virtue of its preformed shape,or it may assume axial curvature by virtue of its preformed shape andradial curvature by virtue of interaction with the adventitia asdescribed previously.

Detailed Examples of Re-Entry Embodiments

As described above, the concave side of a subintimal device with aradial bend is consistently toward the true lumen. A re-entry device maythus be predictably directed toward the true lumen (without employingcomplex visualization techniques) by aligning itself with respect to theconcave side of the radial curve of the subintimal device. Therefore, inthe following embodiments, various re-entry devices are illustrated thatalign themselves relative to the concave side of a radial bend in asubintimal device to establish predictable re-entry into the true lumen(without employing complex visualization techniques).

FIGS. 23A-23E show embodiments of re-entry devices that may be advancedthrough a lumen within a subintimal device 2300. The subintimal device2300 may be similar to the devices described previously to facilitateformation of a radial bend with a concave side oriented toward the truelumen 116 distal of a total occlusion. With reference to FIG. 23A,subintimal device 2300 may be positioned within the subintimal space 130between the intimal 113 and medial 115 layers. A radial curve may beformed in the subintimal device 2300 using any of the methods describedpreviously, and the radial curve may be less than the radial curvatureof the artery. A radial curvature with a diameter less than the insidediameter of the artery causes the tip of the subintimal device 2300 tobe pointed toward the true lumen 116. The re-entry device 2310 maycomprise a guide wire, a sharpened stylet or the like to facilitatepenetration through the intimal layer. Advancement of the re-entrydevice 2310 though the central lumen within the subintimal device 2300and out the distal end results in penetration through the intimal layer113 and into the true lumen 116.

An alternative re-entry embodiment is shown in FIG. 23B wherein thesubintimal device 2300 has a radial curvature approximating the insidecurvature of the artery. The subintimal device may be placed within thearterial wall between intimal 113 and medial 115 layers as describedpreviously. In this embodiment, the re-entry device 2310 may have apreformed bend that is less than the curvature of the subintimal device2300 and less than the inside curvature of the artery. The re-entrydevice is longitudinally and rotationally movable with respect to thesubintimal device 2300, thus allowing the curvature of the re-entrydevice 2310 to self-align with the curvature of the subintimal device2300. Thus, with the concave side of the curved subintimal deviceoriented toward the true lumen, the concave side of the curved re-entrydevice 2310 will also be oriented toward the true lumen. Advancement ofthe re-entry device 2310 through the subintimal device 2300 and out thedistal end thereof results in penetration through the intimal layer 113and into the true lumen 116. Because the curvature of the re-entrydevice is less than the inside curvature of the artery, the tip of there-entry device remains in the true lumen and does not engage theopposite wall of the artery.

Another alternative re-entry device embodiment is shown in FIG. 23Cwherein the re-entry device 2310 exits out a distal side port 2302 inthe subintimal device 2300. The side port 2302 may be located on theconcave side of the curvature of the subintimal device 2300 thusorienting the tip of the re-entry device 2310 toward the true lumen 116.In this embodiment, the re-entry device 2310 may have a slight bend atits distal end to bias the tip toward the port 2302 such that it exitsthe port upon advancement.

Another alternative re-entry device embodiment is shown in FIGS. 23D and23E. FIG. 23E is a cross sectional view taken along line A-A in FIG.23D. In this embodiment, the subintimal device 2300 and the re-entrydevice may be provided with radial curvature for orientation toward thetrue lumen 116 as described previously. In addition, a portion of thesubintimal device 2300 such as the tip 2304 and a distal portion of there-entry device 2310 may be provided with a mating or keying geometry tofacilitate relative alignment. Various non-circular mating geometriesmay be used, including a rectangular cross section as shown in FIG. 23E.

FIGS. 24A-24C show various embodiments of penetrating tips for use on are-entry device. As mentioned previously, the re-entry device 2310 maycomprise a guide wire or the like to facilitate penetration through theintimal layer 113 from the subintimal space 130 to the true lumen 116.Alternatively, the tip of the re-entry device 2310 may be designed toenhance penetration through the intimal layer 113, particularly in thecase where the intimal layer is diseased. If the intimal layer 113 isdiseased, it will likely be tougher than healthy tissue because it maycontain soft plaque, fibrous plaque and/or hard calcified plaque. Thepresence or absence of disease at the intended re-entry site and thenature of the disease may require a re-entry device capable ofpenetrating the various plaques within a non-homogenous diseasedarterial wall. In the event the re-entry site is free from disease orcontains relatively soft plaque, a conventional guide wire may be usedas a re-entry device. Alternatively, if disease is encountered, the tipconfigurations illustrated in FIGS. 24A-24C may be employed.

As shown in FIG. 24A, the re-entry device may have a rotational cuttingor piercing element 2410 capable of penetrating the arterial wall. Therotational element 2410 may, for example, be similar to a timed drillbit. Rotation of the re-entry device with rotational cutting element2410 may be achieved through manual manipulation by the physician orthrough a powered mechanism such as an electric motor.

As shown in FIG. 24B, the re-entry device may have a rotational abrasiveelement 2420. The abrasive element 2420 may include an abrasive coatingsuch as 220 grit diamond abrasive. The abrasive coating may be appliedto the tip of the re-entry device through an electroplating process.Rotation of the re-entry device with rotational abrasive element 2420may be achieved through manual manipulation by the physician or througha powered mechanism such as an electric motor.

As shown in FIG. 24C, the re-entry device may have a tapered orsharpened tip 2430. The sharpened tip 2430 may penetrate the intimallayer 113 through axial advancement or axial reciprocation. The end ofthe re-entry device, for example, may taper to a sharp point. Axialmovement or reciprocation of the tapered or sharpened tip 2430 may beachieved through manual manipulation by the physician or through apowered mechanism such as an electric motor or a solenoid.

Confirmation of a re-entry device entering the true arterial lumendistal of the occlusion may be difficult through the sole use oftwo-dimensional images obtained via fluoroscopy. These two-dimensionalimages may allow a physician to determine if a re-entry device is inclose proximity to the artery, but may not offer adequate resolution todetermine precise position (i.e. within the artery wall vs. within thetrue arterial lumen). Confirmation of true lumen re-entry may beachieved by understanding when the re-entry and/or the subintimal devicepenetrate the intimal layer 113 and come in contact with the blood inthe true lumen 116 distal to the total occlusion.

One method of determining if the true arterial lumen has been accessedis by drawing intra-arterial blood from the distal entry pointproximally through a lumen within the re-entry device or a lumen withinthe subintimal device to the proximal end of the device where thepresence of blood may be detected. This method takes advantage of thefact that there is typically blood in the true lumen distal of theocclusion but there is little to no blood in the subintimal space. Thus,the absence of blood indicates the device is subintimal and the presenceof blood indicates the device is in the true lumen. This technique mayalso be used to indicate perforation of the device out of the artery andinto the pericardia! space by the presence of pericardial fluid.

FIG. 25 illustrates a re-entry device 2500 that facilitates confirmationof true lumen re-entry. The re-entry device 2500 may be passed through asubintimal device 2300, oriented toward the true lumen 116, andpenetrate the intimal layer 113 from the subintimal space 130 to thetrue lumen 116 as described previously. In this embodiment, the re-entrydevice 2500 is provided with an internal lumen extending from itsproximal end to a distal opening 2502. The proximal end of the re-entrydevice 2500 is connected to an indicator 2504 which is in turn connectedto a vacuum source. The indicator 2504 may be a flow indicator such as acollection vessel where the presence and type of fluid may be visuallyobserved. With the vacuum source generating a negative pressure, entryof the re-entry device 2500 into the true lumen 116 allows blood to flowinto the distal opening 2502 and through the internal lumen to theindicator 2504. Alternatively, the vacuum source and indicator may befluidly attached to the subintimal device where entry of the device intothe true lumen results in similar blood flow into the indicator.Alternative indicators 2504 may be employed such as impedance sensors,oxygen sensors, optical sensors, etc.

Detailed Examples of Deployable Element Embodiments

Various devices have been previously described herein that aredeployable in the subintimal space for a variety of purposes. Thefollowing embodiments are additional examples of such deployable devicesthat may be used in the same or similar manner. For example, thefollowing embodiments provide a deployable element that when releasedwithin the subintimal space along the length and around thecircumference of the total occlusion may serve as: (i) a visualizationaid that may help define the arterial wall during fluoroscopy; (ii) aprotective element that may guard the exterior vessel layer or layersfrom devices passing through the total occlusion within the truearterial lumen; and/or (iii) a protective element: that may provide anindication of close proximity or contact between a device passed throughthe total occlusion within the true arterial lumen and the protectiveelement. The deployable element may be readily released from andrecaptured into an exterior containment sheath. The deployable elementmay also be released and remain deployed within a patient as a permanentimplant. This permanent implant may serve as a stent and/or may alsoelute a drug.

An example of a deployable element 2600 is schematically illustrated inFIG. 26A. The deployable element 2600 may be disposed about a subintimaldevice 2300 and contained thereon by a retractable containment sheath2610. In FIG. 26A, the deployable element 2600 is shown in the processof release from its constrained position by the proximal refraction ofthe containment sheath 2610. The deployable element 2600 may comprise,for example, a collapsible lattice structure that is capable ofexpanding from a first collapsed configuration within the containmentsheath 2610 to a second deployed configuration upon retraction of thesheath 2610 that allows it to expand within the arterial wall. In thisembodiment, the deployable element 2600 is shown in the submedial spacebetween the media 115 and adventitia 117. FIG. 26B shows the deployableelement 2600 completely released from the subintimal device 2300 bycomplete retraction of the exterior containment sheath 2610. Thedeployable element 2600 may expand around the circumference and alongthe length of a total occlusion (not shown) thus concentricallysurrounding a diseased segment. The lattice structure of the deployableelement 2600 may be made of a material capable of withstanding strainbetween the collapsed configuration and the deployed configurationwithout significant permanent deformation. Suitable materials for thedeployable element 2600 include but are not limited to nickel titanium,stainless steel, elgiloy, or MP35N.

The deployable element may be used to aid in defining the arterial wallin the area of a total occlusion. As known to those skilled in the art,a totally occluded artery may not allow sufficient radiopaque contrastsolution to penetrate the diseased segment thus preventing a physicianfrom visualizing the artery in the occluded area. Placing a deployableelement of sufficient radiopacity (as seen via fluoroscopy) within thearterial wall around a total occlusion may allow a physician tovisualize the occluded segment. Visualization of the artery in the areaof occlusion may allow subsequent interventional devices (i.e. guidewires, balloons, stents, etc.) to be successfully passed within theconfines of the deployable element.

The deployable element may alternatively provide mechanical protectionfor the arterial layers concentrically outward of the deployable elementfrom crossing devices intended to penetrate the total occlusion such asguide wires, atherectomy devices, laser ablation devices, andradiofrequency ablation devices. For example, FIG. 27 shows a rotationalabrasive device 2700 with an abrasive cutting tip 2710 passing through atotal occlusion 120 with the deployable element 2600 protecting thearterial wall from perforation. While the abrasive tip 2710 is effectiveat passing through the total occlusion 120, the deployable elementcomprises a relatively harder material (e.g., metallic) with a latticepattern having openings smaller than the tip 2710 to prevent perforationtherethrough.

The deployable element may alternatively provide vessel wall protectionby indicating when the occlusion crossing device (guide wire,atherectomy device, laser ablation device, and radiofrequency ablationdevice, etc.) is in close proximity to or in contact with the vesselwall. For example, either the distal end of the deployable element orthe distal end of the crossing device may act as a transmitting antennaand the other of the two may act as a receiving antenna. Thetransmitting antenna may be electrically connected to a radiofrequency(RF) signal generator and the receiving antenna may be connected to anRF signal receiving or detection circuit via a lengthwise insulatedand/or shielded lead disposed in each of the devices. As an alternativeto RF proximity detection, impedance may be similarly used as anindicator of proximity.

With either an RF or impedance based approach, a relatively weak signalis indicative of the crossing device being further away from thedeployable element, for example when the crossing device is in thecenter of the occluded artery. A relatively stronger signal isindicative of the crossing device being in close proximity to thedeployable element, for example within the subintimal space. Thephysician may use this proximity information to safely and effectivelydirect the crossing device within the confines of the deployable elementand across the total occlusion within the true arterial lumen.

As an alternative to a lattice structure described previously, thedeployable element 2800 may comprise one or more continuous elasticmembers as shown in FIG. 28. The deployable element 2800 may be releasedfrom an exterior containment sheath (not shown) as described previouslyto expand circumferentially within the subintimal space. As shown inFIG. 28, the deployable element 2800 may comprise a single continuouspreformed elastic wire with an atraumatic tip located at the distal endof the wire form to reduce the potential for unintended vessel walldamage. The wire may be made of suitable elastic materials that includebut are not limited to nickel titanium, stainless steel, elgiloy, orMP35N. This wire form may include multi-axis bends approximating asinusoidal pattern bent around a cylinder. The diameter of thecylindrical shape may be selected to match the inside diameter of theartery. The wire form may be restrained in a relatively straightconfiguration when placed within an exterior containment sheath foradvancement through the vasculature to the intended deployment site.Upon withdrawal of the containment sheath, the wire form may assume theaforementioned multi-axis shape.

The deployable element may also be used to orient a re-entry devicetoward the true lumen distal of the total occlusion. For example, asubintimal device 2900 may have an accessory deployable element 2910 asshown in FIGS. 29A-29D, FIGS. 29B and 29D are cross sectional end viewsof FIGS. 29A and 29C, respectively. With reference to FIGS. 29A and 29B,the subintimal device 2900 is shown positioned in the subintimal spacewith the accessory deployable element 2910 having an exposed portiondisposed in a recess and a proximally extending portion in a lumen ofthe subintimal device 2900. With reference to FIGS. 29C and 29D,advancing the proximal portion of the deployable element causes theexposed portion to protrude from a side port 2904 and advance within thesubintimal space. The geometry of the deployable element may be apreformed shape such as a U-shape to allow atraumatic expansion withinthe subintimal space as shown. With the accessory deployable element inthe subintimal space as shown, it forms a radial curvature with aconcave side that faces the true lumen 116. With the concave side facingthe true lumen, a re-entry device may be directed to penetrate theintimal layer into the true lumen as previously described with referenceto FIGS. 23A-23E, 24A-24C, and 25.

Occlusion Removal Embodiments

Some of the devices described herein may also be used to facilitatecomplete or partial removal of a total occlusion, potentially includingan inner portion of the arterial wall. FIGS. 30A-30D illustrate anexample of this application wherein a delivery device 400 is used todeliver a subintimal device 300 around a total occlusion 120, similar towhat is shown and described with reference to FIGS. 4, 4A, 4B and 5. Theocclusion is then removed as will be described in more detail.

With reference to FIG. 30A, the delivery device 400 is positioned justproximal of a total occlusion 120. In this position, the balloon 404 maybe inflated within the vessel lumen 116 to direct the delivery tube 414toward the vessel wall 118 at an orientation for the subintimal device300 to penetrate through the intima 113 at an entry point and into thesubintimal space. By virtue of the helical delivery tube 414, thesubintimal device 300 is sent on a helical trajectory as it is advancedthrough delivery tube 414 resulting in deployment of the subintimaldevice 300 in a helical pattern. As shown, the subintimal device 300 hasbeen advanced through the delivery tube 414 and positionedconcentrically outside the total occlusion 120, outside the intimallayer 113, and inside the medial layer 115 in the subintimal space.

With reference to FIG. 30B, a subintimal device capture catheter 3010 ispositioned across the chronic total occlusion 120 over a conventionalguide wire 700 and within the subintimal device 300. The proximal 301and distal 303 ends of the subintimal device 300 have been captured androtated by capture device 3010 so as to reduce the outside diameter andcontain the lesion 120 and intima 113 within the coils of the subintimaldevice 300.

With reference to FIG. 30C, a tubular cutting device 3020 with asharpened leading edge may be advanced over the subintimal device 300and the capture device 3010 to engage and cut the intimal layer 113 withthe total occlusion 120 therein. With reference to FIG. 30D, furtheradvancement of the cutting device 3020 cuts and separates the diseasedportion including the total occlusion and surrounding intima from theremainder of the artery. Proximal withdrawal of the device from theartery results in removal of the total occlusion and a patent true lumen116. The occlusion 120 may be removed through the percutaneousintravascular access site or a surgical cut down may be performed tofacilitate removal if the occlusion is too large for removal through thepercutaneous access site. Alternatively, to reduce the size of theocclusion and thus facilitate removal through the percutaneous accesssite, a maceration mechanism may be employed to macerate the occlusionprior to removal.

In addition or as an alternative, a corkscrew-type device 3110 may beused to grasp and pull the total occlusion 120 for removal as shown inFIGS. 31A and 31B. It is contemplated that corkscrew-type device 3110may be used in combination with the devices described with reference toFIGS. 30A-30D which are not shown for sake of clarity. With reference toFIG. 31A, the corkscrew device 3110 is shown with an exterior sheath3120. The corkscrew device 3110 is shown engaging occlusion 120 afterdelamination of the intimal layer 113 has been performed by theaforementioned methods and devices. FIG. 31B shows removal of theocclusion 120 and a portion of the intimal layer 113 through axialwithdrawal of the corkscrew device 3110.

Alternative Bypass Embodiment

FIGS. 32A-32E illustrate an alternative system for bypassing a totalocclusion. With reference to FIG. 32A, a subintimal device 3200 is shownin the deployed configuration. The subintimal device 3200 includes anelastic wire 3210 with a distal form similar to the elastic wire form2800 described with reference to FIG. 28, except with fewer sinusoidalturns. The subintimal device also includes a crescent-shaped orsemi-circular delivery shaft 3220 and a retractable constraining sheath3230. As seen in FIG. 32B, which is a cross-sectional view taken alongline A-A in FIG. 32A, the wire 3210 resides in the recess of thesemicircular delivery shaft 3220 over which the constraining sheath 3230is disposed. As an alternative, the constraining sheath 3230 may bedisposed about the wire 3210 only and may reside in the recess of thedelivery shaft 3220, provided that the constraining sheath 3230 issufficiently stiff to at least partially straighten the formed wire3210. The distal end of the wire 3210 is connected to a blunt tip 3222of the shall 3220. The wire 3210 and the semi-circular shaft 3220 may beformed of a resilient metallic material such as nickel titanium,stainless steel, elgiloy, or MP35N, and the sheath 3230 may be formed ofa flexible polymeric material such as a polyether-block-amide (e.g.,Pebax) lined with PTFE (e.g., Teflon).

Pulling the wire 3210 proximally relative to the shaft 3220 andadvancing the sheath 3230 over the wire form constrains the wire form inthe recess and renders the device 3200 suitable for atraumatic passagethrough the subintimal space. Once the device 3200 is positioned acrossthe total occlusion within the subintimal space, the sheath 3230 may beretracted relative to the shaft 3220 to release the formed portion ofthe wire 3210. Releasing the wire form causes it to extendcircumferentially around the occlusion in the subintimal space as shownin FIG. 32C. Once the wire form is fully deployed in the subintimalspace, the sheath may be completely removed.

As shown in FIG. 32D. with the wire form 3210 deployed in the subintimalspace and with the sheath 3230 removed from the shaft 3220, a dual lumenre-entry delivery catheter 3250 may be advance over the shaft 3220. Asseen in FIG. 32E, which is a cross-sectional view taken along line A-Ain FIG. 32D, the delivery catheter 3250 includes a crescent-shaped orsemi-circular lumen 3254 that accommodates the shaft 3220 extendingtherethrough. The delivery catheter 3250 also includes a circular lumen3252 that accommodates a re-entry device 3240 extending therethrough.The delivery catheter 3250 may comprise a dual lumen polymeric extrusionsuch as polyether-block-amid (e.g., Pebax) and the reentry device 3240may be the same or similar to the re-entry devices described previouslyherein.

Alternatively, the delivery catheter 3250 may comprise two coaxial tubesincluding an elongate inner tube disposed in an elongate outer tube. Theinner tube is configured to accommodate a re-entry device. The annularlumen defined between the inner tube and the outer tube is configured toaccommodate semicircular delivery shaft 3220. At the distal end of thedelivery catheter 3250, the inner tube may be tacked to the inside ofthe outer tube using a heating forming process where a portion of theoutside circumference of the inner tube is thermally fused to the insidecircumference of the outer tube thus creating a cross section similar tothat shown in FIG. 32E over the heat formed area. Outside the heatformed area, the inner and outer tubes may remain coaxial and un-fused.

As described previously, the concave side of the wire form faces thetrue lumen, and with the fixed attachment of the wire 3210 to the tip3222 of the shaft 3220, the concave side of the semi-circular shaft 3220also faces the true lumen. This feature may be used to facilitateorientation of a re-entry device toward the true lumen. For example,because lumen 3252 of the delivery catheter 3250 has a mating or keyedgeometry with the semi-circular shaft 3220, and because the concave sideof the semi-circular shaft 3220 is oriented toward the true lumen, there-entry device lumen 3252 may be oriented toward the true lumen aswell. With this in mind, any of the re-entry device orientation methodsdescribed with reference to FIGS. 23A-23E may be employed. As shown inFIG. 32D, the distal end of the semi-circular shaft 3220 has a curvaturewith a concave side facing the true lumen which may be used in concertwith a curved re-entry device 3240. Once orientation is established, there-entry device 3240 may penetrate the intimal layer 113 and re-enterthe true lumen as shown.

From the foregoing, it will be apparent to those skilled in the art thatthe present invention provides, in exemplary non-limiting embodiments,devices and methods for the treatment of chronic total occlusions.Further, those skilled in the art will recognize that the presentinvention may be manifested in a variety of forms other than thespecific embodiments described and contemplated herein. Accordingly,departures in form and detail may be made without departing from thescope and spirit of the present invention as described in the appendedclaims.

What is claimed is:
 1. A method of facilitating treatment via a vascularwall defining a vascular lumen containing an occlusion therein, themethod comprising: providing a first intravascular device having adistal portion with a keying element; providing a re-entry device havinga keyed distal portion; inserting the first intravascular device intothe vascular lumen; positioning the distal portion of the firstintravascular device in the vascular wall; orienting the distal portionof the first intravascular device toward the vascular lumen; andorienting the keyed distal portion of the re-entry device with respectto the keying element of the first device such that the re-entry deviceis oriented toward the vascular lumen.
 2. The method of claim 1, whereinthe distal portion of the first intravascular device includes a radialcurve having a radius of curvature that is less than a radius ofcurvature of the vascular lumen.
 3. The method of claim 2, wherein thekeyed distal portion of the re-entry device includes a radial curvehaving a radius of curvature less than a radius of curvature of thevascular lumen.
 4. The method of claim 1, wherein the distal portion ofthe first intravascular device includes a radial curve having a radiusof curvature approximating the curvature of the vascular lumen.
 5. Themethod of claim 1, wherein positioning the distal portion of the firstdevice comprises traversing the occlusion with the distal portion of thefirst device, and further comprising penetrating the vascular wall withthe re-entry device toward the vascular lumen.
 6. The method of claim 1,wherein the keyed distal portion of the re-entry device includesexternal surface features configured for engagement with surfaces alongan internal lumen of the keying element.
 7. The method of claim 1,wherein the keying element of the first intravascular device engages thekeyed distal portion of the re-entry device to prevent relative rotationbetween the first intravascular device and the re-entry device.
 8. Themethod of claim 1, wherein the keying element of the first intravasculardevice includes a non-circular lumen portion and the keyed distalportion of the re-entry device includes a non-circular portionconfigured to be positioned in the non-circular lumen.
 9. The method ofclaim 1, further comprising: advancing the re-entry device relative tothe first intravascular device to penetrate the vascular wall with there-entry device.
 10. The method of claim 9, further comprising:advancing the re-entry device into the vascular lumen distal of thefirst intravascular device.
 11. A method of facilitating treatment via avascular wall defining a vascular lumen containing an occlusion therein,the method comprising: inserting an intravascular device into thevascular lumen; positioning a distal portion of the intravascular devicein the vascular wall; advancing the distal portion of the intravasculardevice distally within the vascular wall until the distal portion of theintravascular device is located beyond the occlusion; advancing are-entry device through a lumen of the intravascular device to penetratethe vascular wall with the re-entry device; and advancing the re-entrydevice into the vascular lumen distal of the intravascular device;wherein the intravascular device includes a keying element mating with akeyed distal portion of the re-entry device to prevent relative rotationbetween the intravascular device and the re-entry device.
 12. The methodof claim 11, wherein the keying element of the intravascular deviceincludes a non-circular lumen portion and the keyed distal portion ofthe re-entry device includes a non-circular portion configured to bepositioned in the non-circular lumen.
 13. The method of claim 11,wherein the intravascular device includes an elongate tubular shaft andan enlarged distal tip secured to the elongate tubular shaft.
 14. Themethod of claim 13, wherein the elongate tubular shaft defines acircular lumen portion of the lumen of the intravascular device and theenlarged distal tip defines a non-circular lumen portion of the lumen ofthe intravascular device in communication with the circular lumenportion of the elongate tubular shaft.
 15. The method of claim 14,wherein the keying element of the intravascular device includes thenon-circular lumen portion.
 16. The method of claim 15, wherein thekeyed distal portion of the re-entry device includes a non-circularportion configured to be positioned in the non-circular lumen.
 17. Amethod of facilitating treatment via a vascular wall defining a vascularlumen containing an occlusion therein, the method comprising: insertingan intravascular device into the vascular lumen; positioning a distalportion of the intravascular device in the vascular wall; advancing thedistal portion of the intravascular device distally within the vascularwall until the distal portion of the intravascular device is locatedbeyond the occlusion; mating a keyed distal portion of a re-entry devicewith a keying element of the intravascular device to prevent relativerotation between the intravascular device and the re-entry device; andadvancing the re-entry device out of the intravascular device topenetrate the vascular wall with the re-entry device with the keyeddistal portion of the re-entry device mated with the keying element ofthe intravascular device.
 18. The method of claim 17, wherein the keyingelement of the intravascular device includes a non-circular lumenportion and the keyed distal portion of the re-entry device includes anon-circular portion configured to be positioned in the non-circularlumen.
 19. The method of claim 17, wherein rotational movement of there-entry device relative to the intravascular device is prevented whileadvancing the re-entry device out of the intravascular device.
 20. Themethod of claim 17, wherein the intravascular device includes anelongate tubular shaft having a circular lumen portion and a distal tiphaving a non-circular lumen portion in communication with the circularlumen portion of the elongate tubular shaft.